This invention relates to fluid conduits in general and, in particular, to a steam conduit associated with a large steam turbine.
In some large power plants using steam turbines as prime movers, steam flows through several turbine sections having different pressure levels in decending order. For example, it is common to find a high pressure turbine section having its exhaust end connected to an intermediate pressure turbine section which may, in turn, be connected to one or more low pressure turbine sections. These turbine sections may all operate to rotate a single rotor. On the other hand, the turbine sections may have separate rotors and not necessarily be at different operating pressures. The present invention is directed to the transfer of fluid into a large rotating shaft machine downstream from a set of fluid control valves.
One criteria for the design of large rotating shaft prime movers is a limit on the maximum rotor speed which would occur upon sudden and complete loss of load. One factor which will determine the rotor maximum speed is the volume of steam or fluid which is stored in the fluid conduits downstream from the various turbine control valves.
Steam flow in a power plant occurs through large steam conduits which may shift in the axial direction because of pressure forces and thermal expansion. These large steam conduits sometimes are referred to as cross-overs. The pressure forces in large steam conduits are usually of such magnitude as to require balance chambers. Balance chambers are well known in the art and are identifiable as adjunct modules attached to a pipe elbow and fluidly in communication with the pressure inside the pipe elbow. The usual mode of construction in the prior art has included a dished-head cap attached to an adjacent pipe module through a bellows joint. More particularly, the dished-head cap was a curved section having a concave surface facing the pipe elbow. It has been found advantageous for reasons to be yet pointed out to reverse the orientation of the dished-head end cap so that the convex portion of the dished-head end cap substantially faces the pipe elbow.